1997 May 05

9

Philips Semiconductors

Preliminary specification

Multiple voltage regulator with switch

TDA3607

TEST AND APPLICATION INFORMATION

Test information

Fig.5 Test circuit.

(1) Capacitor not required for stability.

handbook, full pagewidth

MBG719

regulator 2

regulator 3

enable input regulator 1

C2

47

µF

C1

220 nF

C3

47

µF

1 k

Ω

5 V

9 V

5 V

regulator 1

C4

47

µF

RL(REG2)

1 k

Ω

RL(REG3)

1 k

Ω

RL(REG1)

6

5

4

2

9

3

8

TDA3607

GND

VP

VP

Ven2

Ven1

enable input regulator 3

enable input regulator 2

1

Ven3

(1)

Application information

Table 1

Noise figures

Note

1. Measured at a bandwidth of 200 kHz.

The noise on the supply line depends on the value of the

supply capacitor and is caused by a current noise (output

noise of the regulators is translated into a current noise by

means of the output capacitors).

REGULATOR

NOISE FIGURE (

at OUTPUT CAPACITOR (

µF)

10

47

100

1

−

150

−

2

−

150

−

3

−

200

−

When a high frequency capacitor of 220 nF in parallel with

an electrolytic capacitor of 100

µF is connected directly to

pins 3 and 8 (supply and ground) the noise is minimal.

The regulators are made stable with the externally

connected output capacitors. The value of the output

capacitors can be selected by referring to the graphs

illustrated in Figs 6 and 7.

When an electrolytic capacitor is used the temperature

behaviour of this output capacitor can cause oscillations at

cold temperature.

The following two examples explain how an output

capacitor value is selected.